The present invention relates to ice-prevention systems for aircraft structures, and more particularly, to an apparatus for measurement of ice thickness employing ultrasonic pulse echo techniques.
The problems relating to the formation of ice on aircraft structures are well known. In certain climatic conditions water droplets may exist at subfreezing temperatures in a liquid state. These supercooled droplets nucleate and form ice upon contact with the aircraft surfaces. Ice therefore tends to form on the leading edges of aircraft structures. The ice can degrade aircraft performance through increasing the effective weight of the aircraft and by increasing drag resistance and reducing lift provided by the airfoils.
Various ice detection devices are well known. In one known detection device, a probe is provided which extends beyond the surface to be monitored. However, the manner of ice accretion on such probe is different from the manner of ice accretion on the surface to be monitored. Hence, the accretion rate on the probe will be higher than the accretion rate on the surface to be monitored.
In another known device, the ice thickness is measured by the changing capacitance of a surface capacitor due to the dielectric properties of the ice which has accreted on the probe. One problem with this latter class of devices is that in order to accurately interpret the data received from the probe, the type of ice (rime, glaze, or mixed) must be known to the user.
It is therefore an object of the present invention to provide an apparatus for measurement of ice thickness which can be mounted flush with the surface upon which ice accretion thickness is to be measured.
It is another object of the present invention provide an apparatus for measurement of ice thickness which is insensitive to types of ice accreted.
It is yet another object of the present invention to provide an apparatus for measurement of ice thickness which is flush with the surface upon which ice accretion thickness is to be measured and can also measure the rate of ice accretion.
It is a further object of the present invention to provide an apparatus for measurement of ice thickness employing ultra-sonic pulse echo techniques to measure ice accretion thickness and also the rate at which ice is accreted.